Full-order sliding mode control for finite-time attitude tracking of rigid spacecraft

This study addresses an attitude tracking problem for a rigid spacecraft with bounded external disturbances. Attitude dynamics of the rigid spacecraft is modelled by a unit quaternion for global representation. Based on this representation, a novel continuous controller is proposed based on the full-order terminal sliding mode method. The finite-time stability of the closed-loop system is assured by Lyapunov and homogeneous finite-time stability theorems. Moreover, the singularity term in the terminal sliding surface is compensated by an identical item in the feedback control law, and this makes the closed-loop system trajectories converge to the equilibrium in finite-time, and hence a high precision is obtained. Finally, simulation results are presented to illustrate the effectiveness of the proposed controller.